A known seat for a vehicle is equipped with a mechanism for moving a headrest in a vehicle's forward direction for the purposes of protecting the head of a seated occupant in the event of a rear end collision. Such vehicle seat is disclosed in JP2000-211410A and JP2003-54343A.
When an impact is applied to a vehicle from the rear, an upper body of a seated occupant is restrained onto a seatback by means of a seatbelt. However, the head of the occupant that is not restrained may be hurled forward and then be shifted rearward because of a reaction force. At that time, the neck of the occupant may receive the impact. Then, in this case, the headrest is brought to move in a vehicle's forward direction relative to the seatback for the purpose of protecting the head of the seated occupant, thereby reducing the impact applied to the neck of the occupant.
According to the recent headrest apparatus, a possibility of a collision is determined on the basis of a detection result of a distance from a following vehicle, for example. Then, if the possibility of a collision is high, the headrest is driven to move so as to be ready for the eventual collision. Such headrest apparatus requires moving the headrest back to an original position (i.e. fully closed position) in the cases where the collision is avoided, for the purpose of resuming a normal driving. Thus, a structure is proposed for moving the headrest in the vehicle's forward direction by means of an electric driving means such as a motor, and then retracting the headrest to a fully closed position.
However, due to an inadvertent use of the headrest by a user during normal operation of a vehicle, the headrest may not be fully retracted, i.e. not in the fully closed position. In addition, a deterioration of the apparatus such as a decrease of a motor ability may cause the headrest not to be fully retracted.
Since the headrest is constituted to operate in the event of a rear end collision, the headrest is required to automatically return to the fully closed position for the normal driving state. Then, a position sensor, a switch, and the like may be provided for detecting a position of the headrest. When it is detected that the headrest is not fully retracted, i.e. not in the fully closed position, it is considered that the headrest may be brought to move to the fully closed position. However, in this case, a cost increase is inevitable due to an increase of parts such as the position sensor and the switch. In addition, since accuracy is required for the position sensor, the switch, and the like in terms of detection of the position of the headrest, a structure of the apparatus may be complicated.
Thus, a need exists for a headrest apparatus for a vehicle that can relocate a not fully retracted headrest front portion to the fully closed position without increasing the number of parts.